The transport of gaseous, liquid, or solid material through a closed conduit or pipe has long been known in the art of material handling. In those applications wherein at least a portion of the material transported is of an abrasive nature, the occurrence of erosion of the pipe or conduit sidewalls is also well known. This undesirable erosion is commonly experienced throughout the material transport piping, but is most acute in the non-linear pipe segments wherein the flow direction of the abrasive material is altered.
In an attempt to reduce or eliminate the erosion of non-linear pipe segments, past practitioners in the art have developed a wide variety of shaping, diverting, and strengthening strategies which will not be herein described in detail. Suffice to say that one moderately successful strategy has involved the use of a composite pipe segment comprising an inner liner fabricated of an abrasion-resistant material and an outer supporting shell of a more resilient, though less abrasion-resistant, material.
Such a system is well disclosed in U.S. Pat. Nos. 4,199,010 issued to McGuth et al and Re. 31,020 issued to Funk, which to the applicant's mind represent the current state of the art of wear-resistant pipe bends. Funk shows a plurality of discrete wear strips attached to the inside wall of a curved pipe segment. The strips are placed so as to cover the area of the pipe segment most likely to be eroded by the abrasive material being transported. The wear strips of Funk must be arranged individually within the outer pipe shell and each secured in place.
Alternatively, McGuth shows a monolithic ceramic liner of abrasion-resistant material disposed within an outer metal shell and having a bed of refractory material in the annular space therebetween. The outer shells of the McGuth curved pipe segments are formed of a plurality of smaller straight pipe sections which are mitered angularly and assembled into a non-linear shell around the monolithic inner liner.
The use of an inner liner of abrasion-resistant material, while significantly slowing the erosion of the non-linear pipe segment, does not stop the occurrence of significant wear over an extended period of operation. In each of the above prior art designs, the removal and subsequent replacement of the inner erosion-resistant liner proves to be a difficult, and perhaps prohibitively costly, undertaking. In Funk, the individual wear strips must be removed along with the weld beads used for their attachment. The amount of effort involved is comparable to that incurred in fabricating a new non-linear pipe segment and, when the transport system downtime is taken into account, may be more costly than simply replacing the worn pipe segment with a new one. Likewise, the wear-resistant conduit of McGuth requires disassembly of the mitered linear outer shell segments in order to exchange the worn monolithic liner with a new replacement. The fact that the outer shell segments are joined by welding reduces the attractiveness of this replacement strategy to such a level as to make it virtually non-occurring in competitive commerical situations.
The prior art pipe segments therefore, while effectively reducing interior wear through the use of a wear-resistant lining material, are difficult to refurbish as the inner liner eventually does wear. This drawback has been unaddressed in the prior art until the present invention.